This is a revised application for renewal of a research program (DA 05471) which has contributed toward findings that endogenous opioids are important in determining taste and diet preferences in rats and humans. Further, diet preferences were found to predict the nature of the feeding response to morphine. Preferences for dietary fat and saccharin were found to be related to subsequent oral self-administration of ethanol, and saccharin preference was observed to be related to the intravenous self- administration of morphine. Th involvement of opioids in mediating diet and taste preferences, and the apparent predictive nature of these preferences in relation to drug self-administration,, suggests the possibility that high preferences for sweet taste and/or dietary fat may be indicative of a general propensity to self-administer drugs. This proposal outlines a series of behavioral experiments which will provide an in-depth examination of the interactions between diet/taste preferences (partially opioid-mediated) and intravenous drug self-administration. Specifically, the acquisition and maintenance of intravenous self-administration of heroin and cocaine will be examined in rats selected for high or low preference for fat or saccharin. A subsequent experiment will examine the effects of manipulation of diet composition on drug self-administration. In a third experiment, diet preferences will be manipulated via preexposure to high-fat or high-carbohydrate diets; the effects of baseline shifts in diet preference on self-administration will then be assessed. A fourth experiment will examine the effects of drug pre-exposure (sensitization) on the interaction between diet/taste preferences and drug self- administration. The proposed studies represent a logical progression from previous and current research by this research group, and may provide information which will be valuable in determining vulnerability to drug abuse. Further, the information may provide a basis for improved behavioral, dietary and pharmacological management of eating disorders and drug abuse.